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From: karn@envy.bellcore.com (Phil R. Karn)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Mobile TCP/IP (was Re: Can subnets be separated by another net?)
Message-ID: <1990Jul14.002206.4091@bellcore-2.bellcore.com>
Date: 14 Jul 90 00:22:06 GMT
References: <9007121332.AA02890@chiya.bellcore.com> <9007121800.AA01850@xap> <153@tots.UUCP> <269E07C3.604D@intercon.com>
Sender: usenet@bellcore-2.bellcore.com (Poster of News)
Reply-To: karn@thumper.bellcore.com
Organization: Packet Communications Research Group (Bellcore)
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In article <269E07C3.604D@intercon.com>, amanda@mermaid.intercon.com
(Amanda Walker) writes:
|> Maybe Motorola's proposed satellite-based cellular system will be better.
|> 
|> That's it!  We put the core gateways into geosynchronous orbit... :-)

The satellites in Motorola's proposed "Iridium" system would NOT be in
geosynchronous orbit, they would be in low altitude polar orbits. As
such, the system is much more like the Multiple Satellite System (MSS)
that DARPA looked at a few years ago. Dave Mills was one of the
investigators.

Satellites in low altitude orbits move quite rapidly, so this will
present a very interesting problem in routing. On the other hand,
orbits are quite predictable, so at least you can compute your
connectivity matrix at any desired time in the future.

Back in the early days of communications satellites, it was not yet
clear that geostationary was the way to go at that time. Many paper
proposals for fleets of satellites in low earth orbit were made, but
they never went very far because of the limits of the ground station
technology in those days.

Phil